2 1/2 inches deep, so my 16.5-inch barrel would function like a 14-inch barrel.
The anodized aluminum body has a built-in repairable air cylinder and a combination of mounting holes to facilitate rigid mounting in tight spaces: counterbored
tapped through-holes on the bottom and tapped holes on the rear and side with a slip fit dowel hole and slot for precision alignment.
Before rough cutting the buttplate to size, it should be temporarily attached to the stock with counterbored
The finished housing measures 2.375" diameter by 1.625" long and requires a very precise counterbored
through-hole in the center.
With tile bolt closed, the chambered case bead is enclosed by the counterbored
bolt face, the chamber wall of the barrel and the front of the upper receiver that surrounds the barrel shank--all of which are steel.
It's not a bad idea to have the conversion done, considering that the chambers are counterbored
and it's deuced difficult to tell if the firing pin is resting on the rim of a cartridge.
Next, they counterbored
the ID with a special custom-made drilling tool in two progressively larger drill head sizes up to 2.700" dia.
Drill the counterbored
holes for the walnut plugs to cover the drywall screws that hold the cross support (B).
Eighteen such features are supplied in a standard library, including bosses, through holes, countersunk and counterbored
holes, and pockets with straight sides or draft angles.
The bolt face is counterbored
although its wall is interrupted for the passage of a Sako-style extractor.
Some would travel through vents on the sides of the receiver ring, both adjacent to the counterbored
face of the bolt.
The grooved cylinder is counterbored
to better support and encase the head of the rimfire cases.